The present invention relates to carbon-based electrodes and, more specifically, to porous activated carbon material and methods for preparing an activated carbon material for use in making such electrodes. The invention also relates to high power density energy storage devices comprising carbon-based electrodes.
Energy storage devices such as ultracapacitors may be used in many applications where a discrete power pulse is required. Such applications range from cell phones to hybrid vehicles. An important characteristic of an ultracapacitor is the energy density that it can provide. The energy density of the device, which can comprise two or more carbon-based electrodes separated by a porous separator and/or an organic electrolyte, is largely determined by the properties of the carbon-based electrodes.
Carbon-based electrodes suitable for incorporation into high energy density devices are known. For example, high performance carbon materials, which form the basis of such electrodes, can be made from synthetic phenolic resin precursors. However, due to the high cost of the synthetic resins, the cost of such carbon-based electrodes can be high. Accordingly, it would be an advantage to provide a more economical carbon material that can be used to form carbon-based electrodes that enable higher energy density devices.
According to one aspect of the invention, activated carbon material that is suitable for incorporation into carbon-based electrodes for use in ultracapacitors and other high power density energy storage devices is derived from natural non-lignocellulosic materials. By using non-lignocellulosic materials as a precursor for the porous, activated carbon material, economically viable, high power, high energy density devices can be formed. As defined herein, unless expressly defined otherwise, “natural, non-lignocellulosic carbon precursor” means at least one natural, non-lignocellulosic carbon precursor. Likewise, reference to an “inorganic compound” means at least one inorganic compound.
According to a further aspect of the invention, an activated carbon material is prepared by forming an aqueous mixture of a natural, non-lignocellulosic carbon precursor and an inorganic compound, heating the aqueous mixture in an inert or reducing atmosphere to carbonize the carbon precursor, and removing the inorganic compound to produce the activated carbon material.
According to a yet further aspect of the invention, an activated carbon material is prepared by heating a natural, non-lignocellulosic carbon precursor in an inert or reducing atmosphere to form a first carbon material, mixing the first carbon material with an inorganic compound to form an aqueous mixture, heating the aqueous mixture in an inert or reducing atmosphere to incorporate the inorganic compound into the first carbon material, and removing the inorganic compound from the first carbon material to produce a porous, activated carbon material.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the invention as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments of the invention, and are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operations of the invention.